Perivascular adipose tissue (PVAT) has been shown to be an important modulator of vascular function through release of both relaxing and contracting factors. However, the involvement of PVAT in development of endothelial dysfunction is not well understood, yet. We have recently demonstrated that mice lacking adipose triglyceride lipase (ATGL) suffer from severe endothelial dysfunction. Since vessels of these mice are coated with large amounts of PVAT, we speculated that this might potentially contribute to disturbed vascular homeostasis. Therefore, PVAT of wild type (WT) and ATGL knockout mice was characteri-zed in terms of inflammatory as well as oxidative stress. Additionally, we wanted to distinguish between short-term PVAT-mediated effects on vascular function as well as long-term in vivo interference of PVAT with aortic NO/cGMP signaling.